Aluminium base alloys

ABSTRACT

An aluminum-copper entectic alloy which contains 33% copper exhibits the phenomenon of superplasticity but does not have the low density and good corrosion characteristics of conventional aluminium-base alloys. It has now been found that aluminium-base alloys consisting of the elements normally present in either nonheat treatable aluminium-base alloys containing at least 5%Mg or at least 1%Zn or heat-treatable aluminium-base alloys containing one or more of the elements Cu, Mg, Zn, Si, Li and Mn in known combinations, and at least one of the elements Zr, Nb, Ta and Ni in a total amount of at least 0.30% substantially all of which is present in solid solution, are superplastically deformable. The remainder of the superplastically deformable alloy may be the normal impurities and incidental elements known to be incorporated in heat-treatable and non-heat treatable aluminiumbase alloys. Advantageously the alloy contains at least 0.30%Zr and preferably at least 0.40%Zr. The alloys of the invention may in some cases be deformed superplastically under isothermal conditions but it has been found advantageous to heat the alloy quickly to the super-plastic forming temperature and/or allow the temperature to rise whilst the deformation is in progress.

United States Patent 1 Watts et al.

I1 Apr. 8, 1975 ALUMINIUM BASE ALLOYS [75] Inventors: Brian MichaelWatts, l-laverhill;

Edward Frederick Emley, Chalfont Saint Giles; Michael James Stowell,Saffron Walden, all of England [73] Assignee: British Aluminum Company,

Limited, London, England and T.I. (Group Services) Limited, Birmingham,England [22] Filed: July 20, 1972 [21] Appl. N0.: 273,639

[30] Foreign Application Priority Data July 20, 1971 United Kingdom33922/71 July 27, 1972 United Kingdom 33922/72 [52] U.S. Cl. 148/32;75/139; 75/141; 75/142; 75/143; 75/146; 75/147; 148/325 [51] Int. Cl.C22c 21/00 [58] Field of Search 75/138-148; 148/32, 32.5

[56] References Cited UNITED STATES PATENTS 1.782.300 11/1930 Hall etal. 75/142 2,245,167 6/1941 3.020.154 2/1962 3,236,632 2/1966 3,666,4515/1972 Bewlcy 75/147 Primary Examine'rR. Dean Attorney, Agent, orFirmKarl W. Flocks [57] ABSTRACT An aluminum-copper entectic alloy whichcontains 33% copper exhibits the phenomenon of superplasticity but doesnot have the low density and good corrosion characteristics ofconventional aluminium-base alloys. It has now been found thataluminium-base alloys consisting of the elements normally present ineither non-heat treatable aluminium-base alloys containing at least 5%Mgor at least 1%Zn or heat-treatable aluminium-base alloys containing oneor more of the elements Cu, Mg, Zn, Si, Li and Mn in known combinations,and at least one of the elements Zr, Nb, Ta and Ni in a total amount ofat least 0.30% substantially all of which is present in solid solution,are superplastically deformable. The remainder of the superplasticallydeformable alloy may be the normal impurities and incidental elementsknown to be incorporated in heat-treatable and non-heat treatablealuminium-base alloys. Advantageously the alloy contains at least0.30%Zr and preferably at least 0.40%Zr. The alloys of the invention mayin some cases be deformed superplastically under isothermal conditionsbut it has been found advantageous to heat the alloy quickly to thesuper-plastic forming temperature and- /or allow the temperature to risewhilst the deformation is in progress.

13 Claims, No Drawings ALUMINIUM BASE ALLOYS BACKGROUND OF THE INVENTIONIt is know that certain alloys under certain conditions can undergo verylarge amounts 'of deformation without failure, the phenomenon beingknown as superplasiticity and characterised by a high strain ratesensitivity index in the material as a result of which the normaltendency of a stretched specimen to undergo preferential localdeformation (necking") is suppressed. Such large deformation aremoreover possible at relatively low stresses so that the forming orshaping of superplastic alloys can be performed more simply and cheaplythan is possible with even highly ductile materials which do not exhibitthe phenomenon. As a convenient numerical criterion of the presence ofsuperplasticity, it may be taken that a superplastic material will showa strain rate sensitivity (nz-value) of at least 0.3 and a uniaxialtensile elongation at temperature of at least 200%, m-value beingdefined by the relationship a n 6''" where represents flow stress, 1 aconstant, e strain rate and m strain rate sensitivity index.

No known aluminium-base alloy can be superplastically deformed otherthan the Al-Cu entectic composition which contains 33% copper and hasneither the low density nor the good corrosion resistance characteristicof aluminium alloys.

SUMMARY OF THE INVENTION According to one aspect of the presentinvention a superplastically deformable aluminium-base alloy consists ofan aluminium-base alloy selected from non'heat treatable aluminium-basealloys containing at least 5%Mg or at least 1%Zn and heat-treatablealuminiumbase alloys containing one or more of the elements Cu, Mg, Zn,Si, Li and Mn in known combinations and quantities, and at least one ofthe elements Zr, Nb, Ta and Ni in a total amount of at least 0.30%substantially all of which is present in solid solution, the remainderbeing normal impurities and incidental elements known to be incorporatedin the said aluminium-base alloys.

According to another aspect of the present invention a method of makinga superplastically deformable aluminium-base alloy semi-fabricatedproduct comprises casting a liquid alloy having a composition accordingto the immediately preceding paragraph at a temperature of at least 775Cto produce a cell size in the cast alloy not exceeding /.LM andsubjecting the cast alloy to plastic working at a temperature notsubstantially in excess of 550C.

By cell size is meant secondary dendrite arm spacing.

The invention also extends to an aricle shaped by the plastic forming ofan alloy according to the said one aspect of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout this specificationall percentages of elements are given as percentages by weight.

By heat-treatable alloys is meant those classes of alloys in which themechanical properties can be improved by precipitation hardeningtreatments, for example alloys of the Al-Cu, Al-Cu-Mg, Al-Mg-Si and A]-Zn-Mg systems.

By non-heat-treatable alloys is meant those classes of alloys in whichthe mechanical properties cannot be significantly improved byprecipitation hardening treatments, for example alloys of the Al-Mn,Al-Mg and Al-Zn systems.

Of the elements Zr, Nb, Ta and Ni it is preferred to use zirconium (Zr)in the alloy according to the invention as niobium (Nb), tantalum (Ta)and nickel (Ni) have been found to be less effective than zirconium ininducing superplastic behaviour in the alloy. These four elements havelow solubility, high temperature coefficient of solubility and diffuseonly very slowly in aluminium even at temperatures as high as 500C. Whenzirconium only is used in the alloy it is used in a quantity of at least0.30% and preferably of at least 0.40%.

It is believed that the alloys according to the invention owe theirsuperplastic properties to the presence of a supersaturated solidsolution of one or more of the elements Zr, Nb, Ta and Ni in asufficient quatity physically to restrict aluminium grain growth bygiving rise at the temperatures employed for hot forming to a finesub-optical precipitate capable of restricting grain boundary movements.The formation of such a fine sub-optical precipitate has been verifiedin alloys containing each ofthe elements Zr, Nb, Ta or Ni, but it wasnot found with Cr. or Mn.

Zirconium is already known to confer on certain aluminium-base alloysboth grain refinement of the cast alloys and to restrict graincoarsening of the worked alloys. However, the maximum liquid solubilityof zirconium in aluminium at the peritectic temperature is approximately0.11% and additions of zirconium to aluminium alloys do not normallyexceed 0.20%.

Tests carried out on alloys formed from pure grades of aluminium with0.2% and 0.571 zirconium additions did not result in superplasticbehaviour at any temperature of testing in the range 350C to 500C. Testshave shown that an aluminum-manganese alloy also does not deformsuperplastically after the addition of zirconium. These tests indicatedthat for an aluminium-base alloy to be superplastically deformable it isnecessary not only to provide a slow diffusing element such as zirconiumwhich would precipitate in the form of finely dispersed and relativelystable second phase particles from a supersaturated solution during hotforming, but also to provide one or more additional elements whichinhibit recovery processes and allow the alloy to crystallise to anultra fine grain structure, for example by lowering the high stackingfault energy of aluminium, thereby making possible the occurrence ofdynamic recrystallisation during or prior to the hot forming.

These additional elements include Cu, Mg, Zn, Li and Si in suchcombinations and in such quantitites as are commonly used in heattreatable aluminium alloys and Mg and Cu in such combinations andquantities as may be used to produce non-heat treatable alloys of Al-Mgor Al-Zn systems containing at least 5% Mg or at least 1% Znrespectively.

Particular suitable combinations of additional elements include.

a. Cu 1.75

MgO

b. Cu 2.5

MgO

Mn0.25 d. Zn2

tional incidental elements, excluding Pb and Bi, not ex- -Cont1nuedceedmg 0.75%. To improve the machinabllitv of the al- Mg 0.75 to 4 '71Cu O m 3 loys small additions of Pb and/or B1 may be made in Zn 3 w 2quantities up to 0.6% of each and up to 1% in total. 4: 5 When Pb and/orBi are present in the alloy, the total t. Zn 4 w 7.5 /1 quantity ofincidental elements, including Pb and/or Bi,

3: will not exceed l.257(. g. Si 0.4 m 0.9 (/1 The alloys according tothe invention may in some h yet f H W cases be deformed superplasticallyunder isothermal 0 8 pie l0 conditions following prolonged soaking atsuperplastic C to .5 forming temperaure but it has been found advantao 8(Z prefcmbii geous to heat the alloy quickly to the superplastic formingtemperature and/or allow the temperature to rise whilst the deformationis in progress. Under the latter it wiii be appreciated from what haspreviously been conditions elongation values of 800% to 1200% werestated that the additional elements of either h or i when b i d on A]6%C 0 5%Z anoys hi h h d iaiioyed with aiumihium give hoihheai "eaiiibiealloy ously shown elongation values of 500% to 700% after while thefldditiOllili elements Of any one Of the remain- Soaking at the plasticforming temperature and isothering combinations when liiioyed withaluminium g 11 mal deformation. The following table illustrates thedifheat-treatable alloy. Alloys containing the additional ferences i hlt bt i ed by the two forming elements lz may need a higher formingtemperature techniques on four other alloy compositions together rangefor best results e.g. up to 550C. with isothermal data on two furthercompositions.

TABLE A Elongation '7! at forming temperature Alloy Type Approx.Composition* Isothermal test Rapid heating after soaking and/or risingat temperature temperature during test BA 733 Al; 4.5%Zn; 0.8Mg l50 330BS L88 Al: ti /(Zn; .WMg:

l.5/(Cu 540 BS 2L70 Al: 571C111 0.9%Si; 170 300 (Liv/(Mu; (Mi /(Mg AA2219 Al; 6.5'/1Cu: 0.3 /rMn: I40 540 (LP/1v BS M20 A]; 0.7% Mg; (m /(Si;200 288 0.2571Cu BS M20 Al; 7 /(M 250 Al: l0/(Zn 600 AI; 3'/(Zn 360Exclusive of Zirconium at approximately 05' level except for the Al: 792Mg alloy where 0.87: zirconium was present.

It is to be understood that the alloy according to the invention maycontain the impurities normally to be found in heat treatable andnon-heat-treatable aluminum-base alloys and one or more of theincidental elements known to be added to such aluminium-base alloys.These incidental elements include in percentages by weight:

B 0 to 0.05

O to 0.4 when not present as a specified constituent.

Rare earth metals and Mn All the alloys were rapidly cast fromtemperatures in the excess of 850C.

Attempts to determine the dissolved zirconium content in alloysaccording to the invention by wet chemi-,

cal processes have not yet proved entirely satisfactory,

but a suitable content can be assured by casting from,

much higher temperatures than are usual in the production of aluminiumsemi-fabricated wrought products together with the use of more rapidsolidification .of the liquid alloy. Thus, whilst casting temperaturesfor known aluminium wrought alloys are in the range 665C to 725C, thealloy of the present invention is cast by temperatures in the range 775Cto 925C and preferaably above 800C. For best results a castingtemperature in the range 825C to 900C is preferred. Similarly, whilstthe normal solidification rates obtaining in semi-continuous directchill casting result in an average cell size or secondary dendrite armspacing of 40 to uM, the solidification rates of the alloys according tothe invention are designed to be such that the average cell size doesnot exceed 30 uM, and preferably does not exceed 25 uM. In this way theminiumum dissolved zirconium content required, believed to be 0.25%represents 0.2% in excess of the equilib rium solubility of zirconium at500C.

If desired the approximate proportion of dissolved zirconium in an alloyof known total zirconium content can be determined by microprobeanalysis; alernatively optical microscopy can be used to provide a rapidcheck as to whether or not there is a substantial proportion of thezirconium not in solution, the phase ZrAl being easily recoognisable.

When the alloy conains Nb or Ta in place of Zr, a high castingtemperature and fine cell size are required; with Ni in place of Zr ahigh casting temperature is not essential.

To assist in the maintenance of a high level of supersaturatedzirconium, the alloys of the present invention may be prepared by splatcooling or spray casting in known manner or by compacting blown powder.

To illustrate the invention aluminium-base alloys containing copper asan essential alloying element, but containing other optional alloyingelements as will be mentioned, are now described by way of example.

Ordinary commercial aluminium of minimum purity 99.5% may be used forpreparing the alloy but better results are obtained by limiting the ironand silicon content, e.g. by preparing the alloy from high purityaluminium of about 99.85% purity. Metal with purity lower than 99.5%(e.g. 99.3%) has nevertheless given acceptable results.

At a given purity level the adverse effects of iron and silicon areminimised if these elements are present in approximately equal atomicproportions. Thus as good results are obtained from 99.8% aluminium withatomically balanced iron and silicon as from 99.9% aluminium with anFezSi atomic ratio of 1:2 or b 2:1. A 1:1 atomic ratio correspondsalmost exactly to an FezSi ratio of 2:1 by weight, the FezSi willtherefore desirably between 1.521 and 2.521 by weight.

Preferably the copper content is in the range 2.5% to 7% andparticularly in the range 3.5% to 6.5%. For high tensile properties inthe formed or shaped object after subsequent full heat treatment,combined with good rolling properties, a copper content of 5.75% to6.25% may be used. A substantially higher copper content than 7% can betolerated where the alloy is to be extruded rather than rolled or can bepre-extruded prior to rolling, for example up to 10%.

Small amounts of some elements may be tolerated or added with a view ofconferring certain properties on the resulting alloy. Magnesium may beadded in amounts up to about 0.5%; manganese and cadmium may each beadded in amounts preferably not exceeding 0.25%, whilst small amountsranging from 0 to 0.2% of one or more grain refining elements Ti, Ta andSc may be added to assist in obtaining a fine grained cast structure.Germanium may also be added in quantities up to 0.5% to control ageingbehaviour.

To achieve superplasticity it appears to be necessary for the alloy whencast to contain a minimum level of zirconium in supersaturated solidsolution so that the zirconium is then available to precipitate in sucha manner during the hot forming operation as will assist in theproduction or maintenance of a very fine grained structure of averagegrain size below uM similar to that observed in other superplasticmaterials. This minimum content of dissolved zirconium will not beachieved unless the total zirconium content of the metal is at least0.30%, and preferably at least 0.40%.

To obtain superplastic behaviour the copper content should desirablyexceed the solid solubility level at the hot forming temperature. Thusfor forming at a temperature of 400-425C the miniumum copper content isdesirably about 2%.

Hot forming will generally be carried out in the temperature range300500C and preferentially in the range 350-475C.

Although the slow diffusion rate of zirconium in aluminium allows thecast alloy to be hot worked by rolling or extrusion to a considerabledegree without excessive precipitation from the alloy of the zirconiumin excess of saturation (it being on the presence of excess zirconiumthat the capability for subsequent superplastic forming depends) it isclearly desirable to avoid excesive pre-heating of the alloy prior tohot working and to carry out the working operations at tempera turesbelow those at which the precipitation of zirconium is rapid, e.g. inthe range 300C to 500C. If desired the cast metal may be held for sometime at temperatures in the range 300C to 400C prior to hot workingwithout detriment and sometimes with benefit to the final superplasticforming properties.

The hot formed objects may be heat treated to develop maximum tensileproperties, e.g. the components may be solution heat treated for 40 minat 535C, rapidly cooled and then artificially aged (precipitation heattreated) for 6 hr at C. Alternatively, though at some sacrifice in theirfinal properties, the objects may be rapidly cooled after hot formingand then artificially aged.

The alloys are fusion weldable provided they have a magnesium contentnot materially exceeding about 0.25%.

If prepared using high purity aluminium the alloys may be chemicallybrightened and anodised or subjected to other forms of decorativeanodising treatment. For bright anodising the copper content mayusefully be about 2.5%, and the combined content of iron and siliconshould not exceed 0.2%. Alternatively, the alloys may be clad, e.g. withpure aluminium, to improve their corrosion resistance.

By virtue of their superplastic behaviour the alloys may be formed intocomplex shapes with sharp angles by applying air pressure for a fewminutes to the alloy heated to a temperature in the range 300C to 500C.

Reference is now made to the following more specific Examples andexperiments.

EXAMPLE 1 TABLE B 1 Total Zr content Maxim-um elongation (wt%) m-valueNil 127 plastic behaviour 1t will be seen from Table B that forsuperplastic behaviour a minimum total Zirconium content of about 0.3%is required.

EXAMPLE ll In a series of bulge test experiments some 0.030in thicksheets having the composition A1-6'/(Cu-0.471.Zr were submitted to bulgetests at 440C and 455C. The sheet was blown by air pressure through anopen circular die so as to form an unsupported bulge as shown by theresults in Table C.

TABLE C Forming temp Pressure applied Height/dia Time taken (C) (p.s.i.)ratio of (mini bulge EXAMPLE III In other experiments an alloy of thecomposition Al- 6%Cu 0. 5%Zr was rolled and subjected to 200% isothermaldeformation at 400C at a velocity of 0.05 in/- min. Tensile tests werecarried out on specimens taken from the deformed alloy and also afterfull heat treatment on the deformed alloy with the results shown inTable D.

TABLE D Tensile properties at room temperature Condition 0.1% proofU.T.S. /r elong Hardstress MNmZ (on 50 ness MNm-Z (tsl) (tsl) mm g.l.)HV

As deformed 99 (6.4) 190 16 62 12.3) Fully heat treated 40 min at 535C304 437 12 140 water quench (19.7) (28.3)

6 hrs at 170C It will be seen therefore that an alloy of the presentinvention is capable of being superplastically deformed and subsequentlyheat treated to give very attractive tensile properties. By modificationof the ageing cycle LII even higher tensile properties can be obtainedat some sacrifice of elongation. The alloy moreover has high resistanceto both creep and fatigue.

A further advantage of the Al-Cu alloys at present being discussed isthat the superplastic behaviour is not limited to a narrow range oftemperature. Typical resalts from two casts of alloy are shown in TableE.

TABLE E Cast Forming Maximum No. Composition temp C m-value 71 elongAl-fi /lCu-052 /lZr 400 0.45 210 425 0.45 300 450 0.42 320 2 Al-o/(Cu0.50'/1 Zr 400 0.41 410 425 0.41 300 450 0.40 250 The effect ofadditions of titanium or chomium in place of zirconium to an Al-6%Cualloy have been investigated, but even with many tenths per cent of Crand/or Ti present it was only possible to induce at most a marginaldegree of superplasticity in the rolled metal. It appears therefore thatan additive which will grain refine the cast structure or which willhinder grain growth after hot working is not sufficient and thatperformance of both functions by two additives is not sufficient forsuperplasticity to be developed in the absence of the fine sub-opticalprecipitate of the kind produced with Zr. Nb, Ta and Ni but not by Crand Mn.

We claim:

1. A superplastically deformable wrought aluminumbase alloy consistingof 1. an aluminium-base alloy selected from the group consisting of(l-a) non-heat-treatable aluminium-base alloys of aluminium and one ofthe elements selected from the group consisting of Mg and Zn, thequantity of Mg being from 5% to 10% with zero to 0.5% Cu, and thequantity of Zn being from 1% to 15% with zero to 0.5% Mg and zero to0.5% Cu, and

(l-b) heat-treatable aluminium-base alloys of aluminium and one of theelements selected from the group consisting of Cu, Mg, Zn, Si, Li, Mnand mixtures thereof in known combinations and quantities in a totalquantity not exceeding 10%, and

2. Zr in an amount of 0.3% to 0.8% in total content of which at least0.25% is present in solid solution,

3. the remainder of said superplastically deformable alloy being normalimpurities and incidental elements known to be incorporated in saidaluminium-base alloys.

2. A superplastic aluminum-base alloy according to claim 1, wherein said(l-b) heat-treatable aluminiumbase alloy consists essentially ofaluminium and Cu 1.75 to 10 Mg 0 to 2 Si 0 to 1.5 in percentages byweight based on the total composition.

3. A superplastic aluminium-base alloy according to claim 1, whereinsaid (142) heat-treatable aluminiumbase alloy consists essentially ofaluminium and Cu 2.5 to 7 Mg 0 to 0.5

in percentages by weight based on the total composition.

4. A superplastic aluminium-base alloy according to claim 3, in whichthe normal impurities include iron and silicon, the iron content rangingfrom 1.5 to 2.5 times the weight of the silicon content.

5. A superplastic aluminum-base alloy according to claim 1, wherein said(l-b) heat-treatable aluminiumbase alloy consists essentially ofaluminium and Cu 3.5 to 5.5

Mg 0.25 m 1.25

Si 0.25 to 1 Mn 0.25 to l in percentahes by weight based on the totalcomposition.

6. A superplastic aluminium-base alloy according to claim 1, whereinsaid (l-b) heat-treatable aluminiumbase alloy consists essentially ofaluminum and Zn 2 to 8 Mg 0.75 to 4 Cu to 2 in percentages by weightbased on the total composition.

7. A superplastic aluminium-base alloy according to claim 1, whereinsaid (l-b) heat-treatable aluminiumbase alloy consists essentially ofaluminium and Zn 3 to 5.5

Mg 1 to 2 Cu 0 to 0.3 in percentages by weight based on the totalcomposition.

8. A superplastic aluminium-base alloy according to claim 1, whereinsaid (l-b) heat-treatable aluminiumbase alloy consists essentially ofaluminium and Zn 4 to 7.5

Mg 2 to 3 Cu 1 to 2 in percentages by weight based on the totalcomposition.

- 9. A superplastic aluminium-base alloy according to claim 1, whereinsaid (lb) heat-treatable aluminiumbase alloy consists esseptially ofaluminium and Si 0.4 to 0.9

Mg 0.5 to 1 in percentages by weight based on the total composition.

10. A superplastic aluminium-base alloy according to claim 1, whereinsaid l-a) non-heat-treatable aluminium-base alloy consists essentiallyof aluminium and Zn 1 to 15 Mg 0 to 0.5

Cu O to 0.5 in percentages by weight based on the total composition.

11. A superplastic aluminium-base alloy according to claim 1, whereinsaid l-a) non-heat treatable aluminium-base alloy consists essentiallyof aluminium and Mg 5 to 10 Cu 0 to 0.5 in percentages by weight basedon the total composition.

12. A superplastic aluminium-base alloy according to claim 1, containingat lest 0.40% Zr.

13. A superplastic aluminium-base alloy according to claim 1, containingat least one of the following incidental elements, in a total amount notexceeding 1.25

percent by weight.

UNITED STATES. PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,876,474 Dated April 8 l975 Inventor(s) Brian Michael WATTS. EdwardFrederick EMLEY and Michael James STOWELL It is certified thaterror-appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

In column 1, cover page, the first Assignee's name should read: THEBRITISH ALUMINIUM COMPANY LIMITED Signed and Sealdthis Arrest.-

RUTH C. MASON C. MA Arrestin Offi RSHALL DANN ummissiuner nj'latems andTrademarks

1. A SUPERPLASTICALLY DEFORMABLE WROUGHT ALUMINUM-BASE ALLOY CONSISTINGOF
 1. AN ALUMINUM-BASE ALLOY SELECTED FROM THE GROUP CONSISTING OF (1-A)NON-HEAT-TREATABLE ALUMINUM-BASE ALLOYS OF ALUMINIUM AND ONE OF THEELEMENTS SELECTED FROM THE GROUP CONSISTING OF MG AND ZN, THE QUANTITYOF MG BEING FROM 5% TO 10% WITH ZERO TO 0.5% CU, AND THE QUANTITY OF ZNBEING FROM 1% TO 15% WITH ZERO TO 0.5% MG AND ZERO TO 0.5% CU, AND (1-B)HEAT-TREATABLE ALUMINIUM-BASE ALLOYS OF ALUMINIUM AND ONE OF THEELEMENTS SELECTED FROM THE GROUP CONSISTING OF CU, MG, ZN, SI, LI, MNAND MIXTURES THEREOF IN KNOWN COMBINATIONS AND QUANTITIES IN A TOTALQUANTITY NOT EXCEEDING 10%, AND
 2. ZR IN AN AMOUNT OF 0.3% TO 0.8% INTOTAL CONTENT OF WHICH AT LEAST 0.25% IS PRESENT IN SOLID SOLUTION, 2.Zr in an amount of 0.3% to 0.8% in total content of which at least 0.25%is present in solid solution,
 3. the remainder of said superplasticallydeformable alloy being normal impurities and incidental elements knownto be incorporated in said aluminium-base alloys.
 2. A superplasticaluminum-base alloy according to claim 1, wherein said (1-b)heat-treatable aluminium-base alloy consists essentially of aluminiumand Cu 1.75 to 10 Mg 0 to 2 Si 0 to 1.5
 3. A superplastic aluminium-basealloy according to claim 1, wherein said (1-b) heat-treatablealuminium-base alloy consists essentially of aluminium and Cu 2.5 to 7Mg 0 to 0.5
 3. THE REMAINDER OF SAID SUPERPLASTICALLY DEFORMABLE ALLOYBEING NORMAL IMPURTIES AND INCIDENTAL ELEMENTS KNOWN TO BE INCORPORATEDIN SAID ALUMINIUM-BASE ALLOYS.
 4. A superplastic aluminium-base alloyaccording to claim 3, in which the normal impurities include iron andsilicon, the iron content ranging from
 5. A superplastic aluminum-basealloy according to claim 1, wherein said (1-b) heat-treatablealuminium-base alloy consists essentially of aluminium and Cu 3.5 to 5.5Mg 0.25 to 1.25 Si 0.25 to 1 Mn 0.25 to 1
 6. A superplasticaluminium-base alloy according to claim 1, wherein said (1-b)heat-treatable aluminium-base alloy consists essentially of aluminum andZn 2 to 8 Mg 0.75 to 4 Cu 0 to 2
 7. A superplastic aluminium-base alloyaccording to claim 1, wherein said (1-b) heat-treatable aluminium-basealloy consists essentially of aluminium and Zn 3 to 5.5 Mg 1 to 2 Cu 0to 0.3
 8. A superplastic aluminium-base alloy according to claim 1,wherein said (1-b) heat-treatable aluminium-base alloy consistsessentially of aluminium and Zn 4 to 7.5 Mg 2 to 3 Cu 1 to 2
 9. Asuperplastic aluminium-base alloy according to claim 1, wherein said(1b) heat-treatable aluminium-base alloy consists essentially ofaluminium and Si 0.4 to 0.9 Mg 0.5 to 1
 10. A superplasticaluminium-base alloy according to claim 1, wherein said (1-a)non-heat-treatable aluminium-base alloy consists essentially ofaluminium and Zn 1 to 15 Mg 0 to 0.5 Cu 0 to 0.5
 11. A superplasticaluminium-base alloy according to claim 1, wherein said (1-a) non-heattreatable aluminium-base alloy consists essentially of aluminium and Mg5 to 10 Cu 0 to 0.5
 12. A superplastic aluminium-base alloy according toclaim 1, containing at
 13. A superplastic aluminium-base alloy accordingto claim 1, containing at least one of the following incidentalelements, in a total amount not exceeding 1.25 percent by weight.